I did not know this about the aquaclear's (over flowing) Thanks for the tip.

Urban legend. The head space on the AC filters is sufficient and not any different than most HOB's.
I think if you totally plug the media on most HOB's there's a chance of overflow...but imagine the time span of neglect required to totally plug the media. If somebody is that neglectful, they deserve much worse than a wet floor.
It's like saying ...
1) "don't get a canister filter cause if the seal fails it will leak".
2) "don't get that fish cause if you don't feed it in two months it will die."
3) "don't get married cause she'll spend all yer money."
doh

Urban legend. The head space on the AC filters is sufficient and not any different than most HOB's.
I think if you totally plug the media on most HOB's there's a chance of overflow...but imagine the time span of neglect required to totally plug the media. If somebody is that neglectful, they deserve much worse than a wet floor.
It's like saying ...
1) "don't get a canister filter cause if the seal fails it will leak".
2) "don't get that fish cause if you don't feed it in two months it will die."
3) "don't get married cause she'll spend all yer money."
doh

I can assure those interested that number three on the list is no urban legend or Myth.
Gettin married is the quickest way i know to screw up a relationship.

My aquaclear leaked all over my floor in the exact way i described above. It emptied 10g of water from my 20g while I was away at school and nobody cleaned the filter. It caused severe water damage to my hardwood floor the support beams below the floor had to be reinforced and braced because of it. Its not just saying random pieces of information I hear as rumors, this actually happened. And not in a long span of time, I normally visit home to work on my aquarium once a month and I had to skip a visit due to exams and the result of letting it go for 2 months w/o cleaning was a leak.

Its not like any of those things you listed, I did not say to NOT get the aquaclear but to be aware of risks that the design holds. Obviously all filters need to be maintained, even the emperor filters need to be maintained or the biowheel doesnt work properly. However, in the design of both filters, the emporer has a spillway that causes any overflow from blockage to run back into the tank.

If you will be able to maintain a good maintenance schedule then the aquaclear is a great choice, but if you may be away on vacation or business often and might end up skipping a few cleanings, then I would aim for the emporer.

I have both. They are both great filters. One thing I don't like on the AC is that the sponge is at the bottom of the basket and I have to remove all the media to get to the sponge to rinse it out. It's a bit of a pain in the butt especially since I have to stand on a step stool to reach the back of the tank to get to it. Also, I have had the basket lift up a bit causing the Bio-max to lift up out of the water a bit. I do like having the flow control.

On the Bio-wheels I've never had any problem with them stopping. I haven't had to touch them since setting the tanks up. I don't use the cartridges, I bought the media baskets ($3.76 each) and stuff them with quilt batting from Walmart. In front of each basket I have a fine foam sponge made by Rena for the XP series canisters. The batting and sponges get rinsed out in used tank water each water change (alternating sides each week). The location of the media slots makes for quick and easy filter maintenance.

I have both. They are both great filters. One thing I don't like on the AC is that the sponge is at the bottom of the basket and I have to remove all the media to get to the sponge to rinse it out. It's a bit of a pain in the butt especially since I have to stand on a step stool to reach the back of the tank to get to it. Also, I have had the basket lift up a bit causing the Bio-max to lift up out of the water a bit. I do like having the flow control.

On the Bio-wheels I've never had any problem with them stopping. I haven't had to touch them since setting the tanks up. I don't use the cartridges, I bought the media baskets ($3.76 each) and stuff them with quilt batting from Walmart. In front of each basket I have a fine foam sponge made by Rena for the XP series canisters. The batting and sponges get rinsed out in used tank water each water change (alternating sides each week). The location of the media slots makes for quick and easy filter maintenance.

I think most/all HOB power filters have the motor/impeller on the bottom, so (except for cartridge types) mechanical filtration would be first in the bottom - just as with most canisters. I see your point about having to pull the entire contents, however, if done every other week or once a month, everything should be rinsed anyway. I'm not as height challenged and I like the idea of quickly/easily pulling the media out for inspection, changes and servicing.
I was thinking of getting a canister, but now I'm thinking of getting another AC70 (in addition to the one I have) to dedicate for bio-media with Matrix and the other to be more mechanical sponge. Both set at lower flow rates. Cost wise, the two HOB's are less than a typical canister and it gives me similar bio-media capacity as well as filter redundancy.

I have a marineland (penguin though, just smaller) and an Aquaclear 50...I hate my marineland, love my aquaclear. They both have benefits and drawbacks. Marineland's biowheels are picky and dont always keep moving, and once dry beneficial bacteria is dead. Yeah, the biomax rises just above the water level poppping my top, but an easy fix is tape or a weighted object to hold the top down thus pushing it down and keeping it there.

My biggest issue is the gph...with any filter actually I go up in size as the gph needed arent on the filters made for its size...example, I have a 29 gal and my needed gph start at the aquaclear 50 size. And my marineland penguin 150b is below needed even though for a 30 gal. I am using both on my 29 gal, as the marineland couldnt do its job solo.

Well all filters are rated for less than optimal, the usual rule is to turn the water over 5x in an hour so go by GPH rather than the recommended rating. However, note that some fish want less flow and some want more so with some fish u can get away with high gph and others need lower gph.